Open loop control of solenoid coil driver

ABSTRACT

An electronic driver circuit for the open loop control of the energization of a solenoid coil, forming part of an electromagnetic solenoid actuator valve, in response to a control pulse produced by a control circuit and where the predetermined schedules are a function of the inductance and resistance of the coil, the desired peak output voltage from the coil and the desired average holding current through the coil.

This is a continuation of U.S. Ser. No. 07/188,981 filed Apr. 29, 1988now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an automatic transmission primarilyintended for motor vehicle use, and more particularly, to an electronicdriver circuit for the open loop control of the energization of asolenoid coil, forming part of an electromagnetic solenoid actuatorvalve, in response to a control pulse produced by a control circuit andwhere the predetermined schedules are a function of the inductance andresistance of the coil, the desired peak output voltage from the coiland the desired average holding current through the coil.

2. Description of Related Art

Generally speaking, land vehicles require three basic components. Thesecomponents comprise a power plant (such as an internal combustionengine) a power train and wheels. The internal combustion engineproduces force by the conversion of the chemical energy in a liquid fuelinto the mechanical energy of motion (kinetic energy). The function ofthe power train is to transmit this resultant force to the wheels toprovide movement of the vehicle.

The power train's main component is typically referred to as the"transmission". Engine torque and speed are converted in thetransmission in accordance with the tractive-power demand of thevehicle. The vehicle's transmission is also capable of controlling thedirection of rotation being applied to the wheels, so that the vehiclemay be driven both forward and backward.

A conventional transmission includes a hydrodynamic torque converter totransfer engine torque for the engine crankshaft to a rotatable inputmember of the transmission through fluid-flow forces. The transmissionalso includes frictional units which couple the rotating input member toone or more members of a planetary gearset. Other frictional units,typically referred to as brakes, hold members of the planetary gearsetstationary during flow of power. These frictional units are usuallybrake clutch assemblies or band brakes. The drive clutch assemblies cancouple the rotating input member of the transmission to the desiredelements of the planetary gearsets, while the brakes hold elements ofthese gearsets stationary. Such transmission systems also typicallyprovide for one or more planetary gearsets in order to provide variousratios of torque and to ensure that the available torque and therespective tractive power demand are matched to each other.

Transmissions are generally referred to as manually actuated orautomatic transmissions. Manual transmissions generally includemechanical mechanism for coupling rotating gears to produce differentratio outputs to the drive wheels.

Automatic transmissions are designed to take automatic control of thefrictional units, gear ratio selection and gear shifting. A thoroughdescription of general automatic transmission design principals may befound in "Fundamentals of Automatic Transmissions and Transaxles,"Chrysler Corporation Training Manual No. TM-508A. Additionaldescriptions of automatic transmissions may be found in U.S. Pat. No.3,631,744, entitled "Hydromatic Transmission," issued Jan. 4, 1972 toBlomquist, et al., and U.S. Pat No. 4,289,048, entitled "Lock-up Systemfor Torque Converter," issued on Sept. 15, 1981 to Mikel, et al. Each ofthese patents is hereby incorporated by reference.

In general, the major components featured in such an automatictransmission are: a torque converter as above-mentioned; fluidpressure-operated multi-plate drive or brake clutches and/or brake bandswhich are connected to the individual elements of the planetary gearsetsin order to perform gear shifts without interrupting the tractive power,one-way clutches in conjunction with the frictional units foroptimization of power shifts; and transmission controls such as valvesfor applying and releasing elements to shift the gears (instant ofshifting), for enabling power shifting, and for choosing the proper gear(shift point control), dependent on shift-program selection by thedriver (selector lever), accelerator position, the engine condition andvehicle speed.

The control system of the automatic transmission is typicallyhydraulically operated through the use of several valves to direct andregulate the supply of pressure. This hydraulic pressure control willcause either the actuation or deactuating of the respective frictionalunits for effecting gear changes in the transmission. The valves used inthe hydraulic control circuit typically comprise spring-biased spoolvalves, spring-biased accumulators and ball check valves. Since many ofthese valves rely upon springs to provide a predetermined amount offorce, it will be appreciated that each transmission design represents afinely tuned arrangement of interdependent valve components. While thistype of transmission control system has worked well over the years, itdoes have its limitations. For example, such hydraulically controlledtransmissions are generally limited to one or a very small number ofengines and vehicle designs. Therefore, considerably cost is incurred byan automobile manufacturer to design, test, build, inventory and repairseveral different transmission units in order to provide an acceptablebroad model line for consumers.

Additionally, it should be appreciated that such hydraulicallycontrolled transmission systems cannot readily adjust themselves in thefiled to compensate for varying conditions such as normal wear on thecomponents, temperature swings and changes in engine performance overtime. While each transmission is designed to operate most efficientlywithin certain specific intolerance, typical hydraulic control systemsare incapable of taking self-corrective action on their own to maintainoperation of the transmission at peak efficiency.

However, in recent year, a more advanced form of transmission controlsystem has been proposed, which would offer the possibility of enablingthe transmission to adapt itself to changing conditions. In this regardU.S. Pat. No. 3,956,947, issued on May 18, 1976 to Leising, et al.,which is hereby incorporated by reference, sets forth a fundamentaldevelopment in this field. Specifically, this patent discloses anautomatic transmission design which features an "adaptive" controlsystem that includes electrically operated solenoid-actuated valves forcontrolling certain fluid pressures. In accordance with thiselectric/hydraulic control system, the automatic transmission would be"responsive"to an acceleration factor for controlling the output torqueof the transmission during a shift from one ratio of rotation (betweenthe input and output shafts of the transmission) to another.Specifically, the operation of the solenoid-actuated valves would causea rotational speed versus time curve of a sensed rotational component ofthe transmission to substantially follow along a predetermined pathduring shifting.

3. Objects of the Present Invention

It is one of the principal objects of the present invention to provide asignificantly advanced electronically controlled transmission which isfully adaptive. By fully adaptive, it is meant that substantially allshifts are made using closed-loop control (i.e., control based onfeedback). In particular, the control is closed loop on speed, speedratio, or slip speed of either N_(t) (turbine) of the torque converterand N_(e) (engine) or a combination of N_(t) and N_(o) (output) whichwill provide the speed ratio or slip speed. This transmission control isalso capable of "learning" from past experience and making appropriateadjustments on that basis.

Another object of the present invention is to provide an automatictransmission in which the shift quality is maintained approximatelyuniform regardless of the engine size, within engine performancevariations or component condition (i.e. the transmission control systemwill adapt to changes in engine performance or in the condition of thevarious frictional units of the transmission).

It is a more specific object of the present invention to provide asolenoid driver circuit for the open loop control of the energization ofa solenoid coil, forming part of an electromagnetic solenoid actuatorvalve, in response to a control pulse produced by a control circuit andwhere the predetermined schedules are a function of the inductance andresistance of the coil, the desired peak output voltage from the coiland the desired average holding current through the coil.

This application is one of several applications filed on the same date,all commonly assigned and having similar Specifications and Drawings,these applications being identified below.

    ______________________________________                                        U.S.                                                                          Ser. No.                                                                             Title                                                                  ______________________________________                                        187,772                                                                              AN ELECTRONICALLY-CONTROLLED,                                                 ADAPTIVE AUTOMATIC TRANSMISSION                                               SYSTEM                                                                 187,751                                                                              AUTOMATIC FOUR-SPEED TRANSMISSION                                      189,493                                                                              PUSH/PULL CLUTCH APPLY PISTON OF AN                                           AUTOMATIC TRANSMISSION                                                 187,781                                                                              SHARED REACTION PLATES BETWEEN                                                CLUTCH ASSEMBLIES IN AN AUTOMATIC                                             TRANSMISSION                                                           189,492                                                                              CLUTCH REACTION AND PRESSURE PLATES                                           IN AN AUTOMATIC TRANSMISSION                                           188,602                                                                              BLEEDER BALL CHECK VALVES IN AN                                               AUTOMATIC TRANSMISSION                                                 188,610                                                                              PRESSURE BALANCED PISTONS IN AN                                               AUTOMATIC TRANSMISSION                                                 189,494                                                                              DOUBLE-ACTING SPRING IN AN                                                    AUTOMATIC TRANSMISSION                                                 188,613                                                                              PARK LOCKING MECHANISM FOR AN                                                 AUTOMATIC TRANSMISSION                                                 187,770                                                                              SOLENOID-ACTUATED VALVE                                                       ARRANGEMENT OF AN AUTOMATIC                                                   TRANSMISSION SYSTEM                                                    187,796                                                                              RECIPROCATING VALVES IN A FLUID                                               SYSTEM OF AN AUTOMATIC TRANSMISSION                                    187,705                                                                              VENT RESERVOIR IN A FLUID SYSTEM OF                                           AN AUTOMATIC TRANSMISSION                                              188,592                                                                              FLUID ACTUATED SWITCH VALVE IN AN                                             AUTOMATIC TRANSMISSION                                                 188,598                                                                              DIRECT-ACTING, NON-CLOSE CLEARANCE                                            SOLENOID-ACTUATED VALVES                                               188,618                                                                              NOISE CONTROL DEVICE FOR A                                                    SOLENOID-ACTUATED VALVE                                                188,605                                                                              FLUID ACTUATED PRESSURE SWITCH FOR                                            AN AUTOMATIC TRANSMISSION                                              187,210                                                                              METHOD OF APPLYING REVERSE GEAR OF                                            AN AUTOMATIC TRANSMISSION                                              187,672                                                                              TORQUE CONVERTER CONTROL VALVE IN A                                           FLUID SYSTEM OF AN AUTOMATIC                                                  TRANSMISSION                                                           187,120                                                                              CAM-CONTROLLED MANUAL VALVE IN AN                                             AUTOMATIC TRANSMISSION                                                 187,181                                                                              FLUID SWITCHING MANUALLY BETWEEN                                              VALVES IN AN AUTOMATIC TRANSMISSION                                    187,704                                                                              METHOD OF OPERATING AN ELECTRONIC                                             AUTOMATIC TRANSMISSION SYSTEM                                          188,020                                                                              METHOD OF SHIFT SELECTION IN AN                                               ELECTRONIC AUTOMATIC TRANSMISSION                                             SYSTEM                                                                 187,991                                                                              METHOD OF UNIVERSALLY ORGANIZING                                              SHIFTS FOR AN ELECTRONIC AUTOMATIC                                            TRANSMISSION SYSTEM                                                    188,603                                                                              METHOD OF DETERMINING AND                                                     CONTROLLING THE LOCK-UP OF A TORQUE                                           CONVERTER IN AN ELECTRONIC                                                    AUTOMATIC TRANSMISSION SYSTEM                                          188,617                                                                              METHOD OF ADAPTIVELY IDLING AN                                                ELECTRONIC AUTOMATIC TRANSMISSION                                             SYSTEM                                                                 189,553                                                                              METHOD OF DETERMINING THE DRIVER                                              SELECTED OPERATING MODE OF AN                                                 AUTOMATIC TRANSMISSION SYSTEM                                          188,615                                                                              METHOD OF DETERMINING THE SHIFT                                               LEVER POSITION OF AN ELECTRONIC                                               AUTOMATIC TRANSMISSION SYSTEM                                          188,594                                                                              METHOD OF DETERMINING THE                                                     ACCELERATION OF A TURBINE IN AN                                               AUTOMATIC TRANSMISSION                                                 187,771                                                                              METHOD OF DETERMINING THE FLUID                                               TEMPERATURE OF AN ELECTRONIC                                                  AUTOMATIC TRANSMISSION SYSTEM                                          188,607                                                                              METHOD OF DETERMINING THE                                                     CONTINUITY OF SOLENOIDS IN AN                                                 ELECTRONIC AUTOMATIC TRANSMISSION                                             SYSTEM                                                                 189,579                                                                              METHOD OF DETERMINING THE THROTTLE                                            ANGLE POSITION FOR AN ELECTRONIC                                              AUTOMATIC TRANSMISSION SYSTEM                                          188,604                                                                              METHOD OF CONTROLLING THE SPEED                                               CHANGE OF A KICKDOWN SHIFT FOR AN                                             ELECTRONIC AUTOMATIC TRANSMISSION                                             SYSTEM                                                                 188,591                                                                              METHOD OF CONTROLLING THE APPLY                                               ELEMENT DURING A KICKDOWN SHIFT FOR                                           ELECTRONIC AUTOMATIC TRANSMISSION                                             SYSTEM                                                                 188,608                                                                              METHOD OF CALCULATING TORQUE                                                  FOR AN ELECTRONIC                                                             AUTOMATIC TRANSMISSION SYSTEM                                          187,150                                                                              METHOD OF LEARNING FOR ADAPTIVELY                                             CONTROLLING AN ELECTRONIC AUTOMATIC                                           TRANSMISSION SYSTEM                                                    188,595                                                                              METHOD OF ACCUMULATOR CONTROL                                                 FOR A FRICTION ELEMENT                                                        IN AN ELECTRONIC                                                              AUTOMATIC TRANSMISSION SYSTEM                                          188,599                                                                              METHOD OF ADAPTIVELY SCHEDULING A                                             SHIFT FOR AN ELECTRONIC AUTOMATIC                                             TRANSMISSION SYSTEM                                                    188,601                                                                              METHOD OF SHIFT CONTROL DURING A                                              COASTDOWN SHIFT FOR AN ELECTRONIC                                             AUTOMATIC TRANSMISSION SYSTEM                                          188,620                                                                              METHOD OF TORQUE PHASE SHIFT                                                  CONTROL FOR AN ELECTRONIC AUTOMATIC                                           TRANSMISSION                                                           188,596                                                                              METHOD OF DIAGNOSTIC PROTECTION FOR                                           AN ELECTRONIC AUTOMATIC                                                       TRANSMISSION SYSTEM                                                    188,597                                                                              METHOD OF STALL TORQUE MANAGEMENT                                             FOR AN ELECTRONIC AUTOMATIC                                                   TRANSMISSION SYSTEM                                                    188,606                                                                              METHOD OF SHIFT TORQUE MANAGEMENT                                             FOR AN ELECTRONIC AUTOMATIC                                                   TRANSMISSION SYSTEM                                                    188,616                                                                              ELECTRONIC CONTROLLER FOR AN                                                  AUTOMATIC TRANSMISSION                                                 188,600                                                                              DUAL REGULATOR FOR REDUCING SYSTEM                                            CURRENT DURING AT LEAST ONE MODE OF                                           OPERATION                                                              188,619                                                                              UTILIZATION OF A RESET OUTPUT OF A                                            REGULATOR AS A SYSTEM LOW-VOLTAGE                                             INHIBIT                                                                188,593                                                                              THE USE OF DIODES IN AN INPUT                                                 CIRCUIT TO TAKE ADVANTAGE OF AN                                               ACTIVE PULL-DOWN NETWORK PROVIDED                                             IN A DUAL REGULATOR                                                    188,609                                                                              SHUTDOWN RELAY DRIVER CIRCUIT                                          188,614                                                                              CIRCUIT FOR DETERMINING THE CRANK                                             POSITION OF AN IGNITION SWITCH BY                                             SENSING THE VOLTAGE ACROSS THE                                                STARTER RELAY CONTROL AND HOLDING                                             AN ELECTRONIC DEVICE IN A RESET                                               CONDITION IN RESPONSE THERETO                                          188,612                                                                              THROTTLE POSITION SENSOR DATA                                                 SHARED BETWEEN CONTROLLER WITH                                                DISSIMILAR GROUNDS                                                     188,611                                                                              NEUTRAL START SWITCH TO SENSE SHIFT                                           LEVER POSITION                                                         ______________________________________                                          "Commonly assigned application Ser. No. 07/187,772, filed Apr. 29, 1988,     now U.S. Pat. No. 4,875,391 has been printed in its entirety. The figures     and the entire Specification of that application are specifically     incorporated by reference. For a description of the above copending     applications, reference is made to the above mentioned U.S. Pat. No.     4,875,391."

SUMMARY OF THE INVENTION

To achieve the foregoing objects, the present invention provides acomprehensive four-speed automatic transmission system. While thistransmission systems particularly features a fully adaptive controlsystem, the present invention achieves the combination of this controlsystem with a unique four-speed transaxle structure which requires fewercomponents and is smaller than previous four-speed transmission systems.For example, the four-speed transmission system according to the presentinvention is capable of fitting into the space made available for aconventional three-speed transmission system.

Additionally, the four-speed transmission system features an electronicdriver circuit for the open loop control of the energization of asolenoid coil, forming part of an electromagnetic solenoid actuatorvalve, in response to a control pulse produced by a control circuit andwhere the predetermined schedules are a function of the inductance andresistance of the coil, the desired peak output voltage from the coiland the desired average holding current through the coil.

FIG 1 is a block diagram of an adaptive control system for an automatictransmission according to the present invention;

FIG. 2 is a block diagram of the transmission controller for theadaptive control system according to the present invention;

FIGS 3A-I comprise a schematic diagram of the transmission controllershown in FIG. 2; specifically, FIG 3A illustrates a communicationcircuit which provides a serial communication link between thetransmission controller and the engine controller; FIG. 3B illustratedthe microprocessor and peripheral interface circuits; FIG. 3Cillustrates the read only memory and watchdog/reset circuits; FIG. 3Dillustrates the speed and throttle input circuits; FIG. 3E illustratesthe ignition switch input circuits; FIG. 3F illustrates the regulatorand relay driver circuits; FIG. 3G illustrates the solenoid drivercircuits; FIG. 3H illustrates the pressure switch input and test modecircuits; and FIG. 3I illustrates two additional communication circuitsfor the transmission controller;

FIG. 4 is a block diagram of the interface chip shown in FIG. 3B;

FIG. 5 is a block/schematic diagram of the watchdog/reset chip shown inFIG. 3C;

FIG. 6 is an equivalent circuit schematic diagram illustrating howdiodes can be used in an input circuit to take advantage of an activepull-down network in a switched voltage section of a dual regulator toprovide high voltage protection to a microcomputer with an electrostaticdischarge protection circuit;

FIG. 7 is an equivalent circuit schematic diagram illustrating how areset output of a voltage regulator can be used as a system low voltageinhibit;

FIG. 8 is a diagrammatic drawing showing how the output of a throttleposition sensor can be shared between two electronic controllers havingdissimilar ground potentials;

FIG. 9 is a diagrammatic illustration of a circuit for determining thecrank position of an ignition switch by sensing the voltage across thestarter relay coil and holding an electronic device in a reset conditionin response thereto; and

FIG. 10 is an illustration of closed loop and open loop control ofsolenoid coil drivers showing basic differences between the circuits andbasic similarities between the voltage outputs.

ELECTRONICALLY CONTROLLED, ADAPTIVE AUTOMATIC TRANSMISSION SYSTEM

Referring to FIG 1, a block diagram of an adaptive control system 3000according to the present invention is shown. The adaptive control system3000 includes a transmission controller 3010 which is capable of bothreceiving signals from an engine controller 3020 and transmittingsignals to this engine controller 3020. While the transmissioncontroller 3010 may be readily adapted to operate without an electronicengine controller, the transmission controller 3010 according to thepresent embodiment takes advantage of the fact that most automobilestoday include a digital or computer based engine controller whichreceives and processes signals from numerous sensors. For example, FIG.1 shows that both the transmission controller 3010 and the enginecontroller 3020 receive an input signal indicative of the temperature ofthe engine (e.g., the coolant temperature). Other exemplary inputsignals shared by these controllers include one or more signals from theignition switch, a battery voltage level signal, and a signal from thedistributor or other firing angle control mechanism. With respect to theengine controller 3020, this controller will process such signals andtransmit appropriate control or command signals to various components ofthe engine. Typical computer based engine controllers will also generateand transmit advisory signals to a diagnostic alert panel in thepassenger compartment to provide a visual and/or auditory indication ofparticular engine conditions.

As indicated by the reciprocal signal lines, it should be appreciatedthat the transmission controller 3010 includes the capability ofcommunicating with existing engine controllers. For example, it may beadvisable for the transmission controller 3010 to send signals to theengine controller 3020, such as a signal indicating that thetransmission 100 is bout to shift gears. As will be appreciated from thedescription below, the transmission controller 3010 is preferablyprovided with a serial communications interface to permit serial datatransfers to made between the transmission controller 3010 and theengine controller 3020. Additionally, the transmission controller 3010may also provide diagnostic alert capabilities, such as transmittingsuitable advisory signals to the vehicle operator (e.g., "checktransmission").

Another example of some signals which may be shared by the transmissioncontroller 3010 and the engine controller 3020 are those provided by athrottle sensor 3030 and a brake switch sensor 3040. The throttle sensor3030 may be any suitable sensor which will give an indication of thepower demand placed upon the engine by the vehicle operator, such as atransducer which will indicate the present position of the throttle.Similarly, the brake switch 3040 may be any suitable sensor which willgive an indication of the application of the vehicle brake by theoperator, such as a contact switch actuated by the movement of the brakepedal in the vehicle. As will be appreciated from the description below,the transmission controller 3010 includes suitable interface circuitsfor receiving signals from the throttle sensor 3030 and the brake switch3040. Further examples of information shared between the controllers aresignals concerning vehicle type, engine type, manifold absolute pressure(MAP) and load.

One of the primary functions of the transmission controller 3010 is togenerate command or control signals for transmission 100 to thesolenoid-actuated valves 630, 632, 634, 636 contained in the hydraulicsystem 600 of the transmission 100. In FIG. 1, these solenoid-actuatedvalves are lumped into a solenoid block 3050 which is contained within adashed block labeled "Transmission". This Transmission block representsa suitable transmission structure which will operate in conjunction withthe transmission controller 3010, such as the transmission 100 describedabove. Thus, in the transmission 100, the solenoid block 3050 wouldcomprise the solenoid-actuated valves 630, 632, 634 and 636. Similarly,the hydraulic controls block 3060 would comprise other valves containedin the hydraulic system 600, such as the pressure regulator valve 608,the manual valve 604, the T/C control valve 612 and so forth, asdescribed above. Likewise, the friction elements gear box block 3070would comprise the multi-clutch assembly 300 and the gear assembly 500as described above. However, it should be appreciated that the adaptivecontrol system 3000 according to the present invention may be used inconjunction with other suitable transmission structures in theappropriate application.

FIG. 1 also illustrates that the Transmission block includes a PRNODDLsensor block 3080 which is responsive to a gear shift lever that isunder operator control. The PRNODDL sensor block 3080 may be comprisedof one or more suitable sensors which are capable of providing anindication to the transmission controller 3010 of the transmissionoperating mode selected through the manual actuation of the gear shiftlever. In this regard, FIG. 4B of U.S. Pat. No. 4,875,391 shows twocontact switch sensors NS₁ and NS₂ which are mounted to the transmissioncase 102. The sensors NS₁ and NS₂ are mounted in proximity to the manuallever 578 in order to permit a spring loaded pin of these sensors toengage and follow the peripheral track of a cap member 578a of themanual lever 578.

NEUTRAL START SWITCH TO SENSE SHIFT LEVER POSITION

Referring briefly now to FIG. 19 of U.S. Pat No. 4,875,391 shows thatthe sensors NS₁ /RL₁ and NS₂ /RL₂ are each provided with a spring loadedcontact pin, such as pin 3082, which engages the cap member 578a of themanual lever 578. The cap member 578a is formed to permit metal areas ofthe manual lever 578 to extend through the cap member 578a, such asmetal areas 3084. These metal areas 3084 are used to provide anelectrical ground for the sensor. Thus, as shown in the correspondingtable for the figure, each of the sensors NS₁ /RL₁ and NS₂ /RL₂ willproduce a digital low or "Φ" signal when their sensor or contact pin isin physical contact with one of the metal areas (e.g., metal area 3084).For example, in the park "P" position, both of the "NS" contacts ofsensors NS₁ /RL₁ and NS₂ /RL₂ will be grounded, as shown by thecorresponding columns of the table under section heading "PRNODDLMETHOD".

The cap member 578a also includes non-grounded areas which are formedwith trapezoidal shaped grooves, such as groove 3086. These grooves areused in connection with a set of internal contacts within the sensorsNS₁ /RL₁ and NS₂ /RL₂ to create the four-bit digital code shown in thetable for FIG. 19 of U.S. Pat No. 4,875,391. These internal contacts3088 are also illustrated in FIG. 19 of U.S. Pat No. 4,875,391, whichprovides a schematic representation of one of the NS/RL sensors. Whenthe contact pin 3082 of either of the sensors NS₁ / RL₁, NS₂ /RL₂extends into one of the grooves 3086 of cap member 578a, then theinternal "RL" contacts 3088 of that sensor will close and cause thesensor to produce a digital high or "1" signal from the electricalterminals of these contacts. As discussed previously, the internalcontacts 3088 provide a set of reverse light "RL" contacts which areused in connection with the reverse or back-up lights of the vehicle.

In operation, actuation of the gear shift lever will cause a rotation ofthe manual lever 578 to the position selected by the vehicle operator.As the manual lever 578 rotates, the sensors NS₁ / RL₁ and NS₂ /RL₂ willproduce a four-bit code which will correspond to the rotational positionof the manual lever 578. The transmission controller 3010 will thendetermine the mode of operation selected through the four-bit codeproduced by the sensors NS₁ /RL₁ and NS₂ /RL₂.

Referring again to FIG. 1, the transmission controller 3010 receivesinput signals from the PRNODDL sensor block 3080, as well as producesoutput signals to a PRNODDL indicator contained in the passengercompartment. This PRNODDL indicator may, for example, be a suitablelight source or other appropriate indicator for providing the operatorwith a visual indication of the operating mode which has been selected.

FIG. 1 also indicates that a pressure switch block 3090 is connected tothe hydraulic controls block 3060. In connection with transmission 100,the pressure switch block 3080 would comprise the pressure switches 646,648 and 650 (FIGS. 5A-L and 10 of U.S. Pat. No. 4,875,391). As describedabove, each of these pressure switches is adapted to provide a signalindicative of a predetermined pressure level in the correspondingpassageways leading to selected friction elements. Specifically, each ofthese pressure switches provide a digital input signal to thetransmission controller 3010 which will indicate whether or not thispressure level has been reached.

FIG. 1 also indicates that the Transmission block includes a speedsensors block 3100 which is connected tot he friction elements gear box3070. In connection with the transmission 100, the speed sensors block3100 comprises the input or turbine speed sensor 320 and the outputspeed sensor 546 which are both mounted to the transmission case 102.However, as previously indicated, other suitable speed sensor means maybe provided either within or outside of the transmission case 102 inorder to provide the desired input or turbine and output speed signalsto the transmission controller 3010. The speed sensors block 3100 mayalso include a suitable engine speed sensor (e.g. hall effect device).However, if the engine controller 3020 is already receiving such a speedsignal, then this signal could be shared with the transmissioncontroller 3010 to avoid unnecessary duplication.

ELECTRONIC CONTROLLER FOR AN AUTOMATIC TRANSMISSION

Referring to FIG. 2, a block diagram of the transmission controller 3010is shown. The first block is the serial communication interface 3200which has as its function to provide a serial communications link withthe engine controller 3020. This serial communication interface 3200could also be used to provide a serial communication link with otherappropriate microcomputer-based controllers in the vehicle. It shouldalso be understood that a parallel communication could also be used inthe appropriate applications.

In the present embodiment, the serial communications interface 3200utilizes the multiplexing protocol and interface technology of theChrysler Collision Detection ("C² D") Serial Data Bus. This technologyis described in the co-assigned U.S. Pat. No. 4,706,082, entitled"Serial Data Bus For Intermodule Data Communications," which issued onNov. 10, 1987; and U.S. Pat. No. 4,729,458, entitled "Method Of DataArbitration And Collision Detection In A Data Bus," which issued on Jan.12, 1988; and U.S. Pat. No. 4,738,323, entitled "Serial Data Bus ForSerial Communication Interface (SCI), Serial Peripheral Interface (SPI)and Buffered SPI Modes of Operation," which issued on Apr. 19, 1988; andU.S. Pat. No. 4,739,324, entitled "Method for Serial PeripheralInterface (SPI) in a Serial Data Bus," which issued on Apr. 19, 1988;and U.S. Pat. No. 4,742,349, entitled "Method for Buffered SerialPeripheral Interface (SPI) in a Serial Data Bus," which will issue onMay 3, 1988; and in SAE paper No. 860389, entitled "Chrysler CollisionDetection (C.sup. 2 D)--A Revolutionary Vehicle Network," by FrederickO.R. Miesterfield, 1986. These patents and documents are all herebyincorporated by reference.

Another function for the serial communications interface 3200 is toprovide a diagnostic interface with the transmission controller 3010 sothat service information can be provided to a technician as atroubleshooting or maintenance aid. Still another function of the serialcommunications interface 3200 is to provide a convenient data or programaccess route for in-plant testing of the transmission controller 3010during the manufacturing process.

The transmission controller 3010 also includes several other interfacecircuits which are used to receive and condition input signals from thevarious sensors identified above. For example, the transmissioncontroller 3010 includes a block 3210 which contains the interfacecircuits used to receive signals from the speed sensors 3100 and thethrottle sensor 3030. The transmission input speed signal represents theturbine speed N_(t) of the torque converter 110, while the output speedsignal represents the output speed N_(o) of the vehicle. As describedabove, both of these signals are generated by variable reluctancepick-ups (e.g., speed sensors 320 and 526). The engine speed is alsosensed by a suitable sensor, such as a hall effect pick-up in thedistributor of the engine. This technology is described in co-assignedU.S. Pat. No. 4,602,603, entitled "Ignition Distributor-Hall EffectSensor Switching System and Method," which issued on July 29, 1986 whichis hereby incorporated by reference.

The function of block 3210 is to provide input signal conditioning,filtering and conversion of the speed sensor signals to digital logiclevels. In this regard, block 3210 also includes an interface circuitfor the throttle position sensor 3030. Once this signal is properlyconditioned, this information may be shared with the engine controller3020. The throttle position sensor 3030 will give an indication as towhich angular position the throttle blade (means) is in within thethrottle body. As with other appropriate input signals, the throttleposition sensor signal is conditioned and fed through a unity gaindifferential amplifier to provide isolation, as will be described below.

The transmission controller 3010 also includes blocks 3220 and 3230which represents the interface circuits used to receive various inputsignals related to the engine ignition and PRNODDL condition.Specifically, the ignition related signals include a signal J2, and asignal S2. The signals related to the PRNODDL condition include the"neutral start" signal NS₁, and "auxiliary neutral start" signal NS₂, a"first reverse light"signal RL₁ and a "second reverse light" signal RL₂.In accordance with the preferred embodiment, the control methodology isresponsive to the condition that these ignition switch voltage signalsare in. The reason for this is that it is appropriate to hold thetransmission controller 3010 in certain predetermined conditionsdepending on the position of the ignition switch and/or the neutralcontact switch sensor NS₁ and/or the auxiliary contact switch sensorNS₂.

For example, the signal J2 represents the ignition voltage during therun and crank positions, and this signal will generally be either at azero voltage level or at the battery voltage level. The signal S2represents the voltage in the crank position only and is used to providethe necessary voltage for the starter relay coil of the engine. Todetermine when the transmission 100 is in a crank condition the NS₁ orneutral start switch signal is sensed along with the S2 signal to holdthe transmission controller 3010 in a reset condition during crankingdue to the possibility that the battery voltage may drop below levelrequired for proper controller operation.

Referring specifically to block 3230, the PRNODDL condition switchesprovide input signals from the contact switch sensor NS₁, the auxiliarycontact switch sensor NS₂, the first reverse light RL₁ and the secondreverse light RL₂. The PRNODDL switch block 3230 controls the switchingof the reverse lights which are connected in series. When the signalsRL₁ and RL₂ indicate a reverse condition, electrical current from theignition switch J2 is fed through a relay coil which interconnects thereverse lights to battery voltage via the relay contacts thus turning onthe backup lights on the vehicle. The PRNODDL switch block also acts incombination with the two contact switch sensors NS₁ and NS₂ to determinethe shift lever position, as discussed above.

As shown in FIG. 2, the transmission controller 3010 includes a pressureswitch block 3240 which represents the interface circuit used forreceiving and conditioning the pressure level signals from the pressureswitches 3090. Each of the pressure switches provide a digital levelsignal which is either at a zero or battery voltage level depending uponwhether or not a predetermined pressure level has been reached. Thepressure switches are used in conjunction with the low/reverse,overdrive and two/four shift (kickdown) clutch assemblies, and generallycomprise grounding switches located in the manifold assembly 700. Thepressure switch interface circuit 3240 provides input signalconditioning, i.e. filtering and buffering for these signals. Forexample, pull up resistors located in the manifold assembly 700 (SeeFIG. 8 of U.S. Pat. No. 4,875,391 to provide battery voltage whenpressure switch is open are contained in block 3090. The state of eachof the pressure switch signals is transmitted to the transmissioncontroller 3010 to provide feedback information for use in bothmonitoring clutch operation and as an input to the learning logic andmethodology described herein.

The heart of the transmission controller 3010 is contained in the microcore block 3250. The micro core 3250 includes an eight-bit microcomputerunit (MCU), a memory chip for storing the application or operatingprogram used by the MCU, and an interface chip for addressing androuting signals on the various lines used in the micro core busstructure. Thus, for example, several of the signals received from thecontroller's interface circuits are connected to the interface chip,which will then place these signals on the data bus when the chip isproperly addressed by the MCU.

The transmission controller 3010 also includes a watchdog/reset block3260 which provides several circuit functions in conjunction with themicro core 3250. For example, the watchdog/reset circuits 3260 willcontrol the initial start up of the MCU, watch to see if the MCU isproperly functioning, cause a reset of the MCU in response to certainregulator voltage conditions, and provide a frequency divider for thespeed signals. The watchdog/reset circuits 3260 also provide an outputto a relay driver block 3270 which is used to disconnect or tun offelectrical power to the solenoid-actuated valves 630, 632, 634 and 636in the solenoid block 3050 shown in FIG. 1 under predeterminedconditions.

One of the principal functions of the micro core 3250 is to generatecommand or control signals for transmission 100 to the solenoid driverblock 3280. The solenoid driver block includes a separate driver circuitfor the solenoid-actuated valves 630, 632, 634 and 636 contained in thesolenoid block 3050 shown in FIG. 1. These driver circuits generate theelectrical current necessary to operate the solenoid-actuated valves630, 632, 634 and 636 in response to the control signals generated bythe MCU. The solenoid driver block 3280 also includes spike monitorcircuits which verify the operation of the solenoid driver circuits bydetecting the presence of an inductive spike (FIG. 22E of U.S. Pat. No.4,875,391) which occurs when the solenoid coil is de-energized.

The transmission controller 3010 also includes a regulator block 3290and a test mode block 3300. The regulator block 3290 is used to advisethe watchdog/reset circuit 3260 of predetermined conditions relating tothe operation of the regulator, such as a low battery voltage condition,a high battery voltage condition, an overload condition, or an overtemperature condition in the regulator. It is a dual regulator andincludes a 5V, switched output. The test mode block 3300 is used topermit a test mode program to be downloaded into the RAM memory of theMCU for testing the transmission system.

Referring generally to FIGS. 3A-3I, a schematic diagram of thetransmission controller 3010 is shown. Each of the FIGS. 3A-3I generallycorrespond to one of the circuit blocks shown in FIG. 2. Thus, forexample, FIG. 3A illustrates the serial communication interface 3200which provides a serial communication link between the transmissioncontroller 3010 and the engine controller 3020. Similarly, FIG. 3Billustrates the MCU chip Z138 and the interface chip Z135 which formpart of the micro core 3250. The remainder of the micro core 3250 isshown in FIG. 3C which illustrates the EPROM chip Z141 and itsassociated circuitry. It should also be notes that FIG. 3C illustrates awatchdog/reset chip Z127 and associated circuitry, which togethercorrespond to the watchdog/reset circuit 3260. A discussion of thecircuits contained in the watchdog/reset chip Z127 will be presented inconnection with FIG. 5. Similarly, a discussion of the circuitscontained in the interface chip Z135 will be presented in connectionwith FIG. 4.

Continuing with an overview of the schematic diagram for thetransmission controller 3010, FIG. 3D illustrates the speed and throttleinput interface circuits 3210. FIG. 3E illustrates the PRNODDL interfacecircuits 3230 and part of the ignition switch interface circuits 3220.FIG. 3F illustrates the regulator circuit 3290 and the relay drivercircuits 3270. FIG. 3G illustrates the solenoid driver circuits 2880.FIG. 3H illustrates the pressure switch interface circuits 3240. FIG. 3Iillustrates an additional serial communication circuit 3400 and adiagnostic communication circuit 3500.

Referring specifically to FIG. 3A, a schematic diagram of the serialcommunications interface 3200 is shown. This communications interfaceactually provides for two serial communication channels for thetransmission controller 3010. The first serial communication channel3201 is based upon the Chrysler Collision Detection (C² D) technologyidentified above. This technology is embodied in the communications chipZ14 which provides the intelligence to know when it has sent a messageto onto a serial data bus and whether or not it has won access to thebus. This bus comprises the two conductors labeled "(C² D)+" and "(C²D)". It should be noted from the above that this serial communicationsbus comprises a double ended or differential signal transmission linkwith the engine controller 3020 (or any other appropriate controller inthe vehicle which is connected to the bus structure). The communicationsship Z14 receives signals transmitted from the microcomputer chip Z138(shown in FIG. 3B) via its connection to the "PD3" port of themicrocomputer. Similarly, signals are transmitted from thecommunications chip Z14 to the microcomputer chip Z138 via the "PD2"port.

It should be noted that the communications chip Z14 is provided with aclock signal "E**" which is derived from the MCU chip's Z138 systemclock, namely the "E" Clock. As shown in FIG. 3C, two NAND gates Z195are connected in series to double buffer and double invert the E clocksignal. Signal transmissions from the MCU chip Z138 are initiated by theMCU chip Z138 which pulls down a "Control " line of communication chipZ14 via a command signal transmitted from the "PD5" port. However, thecommunications chip Z14 will actually control the transfer of data fromthe MCU chip Z138 by providing a "SCLK" clock signal to the MCU's "PD4"port, which will clock the data in and out of the MCU chip.

It should also be noted that the communications chip Z14 is turned offwhen the transmission controller 3010 is in a stop mode, such as afterthe ignition key is turned off. The communications chip Z14 is turnedoff through the "SW/5V" power supply. The SW/5V voltage level is derivedfrom a dual regulator Z215 contained in the regulator circuit 3290 shownin FIG. 3F. Specifically, the SW/5V supply is switched on or enabled bythe MCU Z138 in response to the ignition switch.

FIG. 3A also illustrated the second serial communications channel whichis generally designated by the reference numeral 3202. The serialcommunications channel 3202 is generally comprised of a transmit linelabeled "SCI-XMT" and a receive line labeled "SCI-REC". Each of thesetransmit and receive lines include an RD filter and a buffering inverterZ15. The transmit line SCI-XMT is connected to the "PD1" port of themicrocomputer chip Z138, while the receive line SCI-REC is connected tothe "PDΦ" port of the microcomputer chip. This second serialcommunications channel may be used for example to download appropriatetest programs into the microcomputer chip Z138, such as for end of linetesting at the manufacturing facility. In one form of the presentinvention, the SCI-REC receive line is used in conjunction with the testmode to transmit a signal to the microcomputer chip Z138 which willcause a ROM resident boot load program inside the microcomputer chip tocontrol the receipt and initial execution of the test programs.

Referring to FIGS. 3B-3C, a schematic diagram of the micro core 3250 isshown. The micro core 3250 for the transmission controller 3010generally comprises the microcomputer 3251 (chip Z138), the interface3252 (chip Z135), and the memory 3253 (chip Z141). In the presentembodiment, the microcomputer chip Z138 is a Motorola eight-bitmicrocomputer chip (Part No. 68HC11), which includes 256 bytes of RAMmemory and 512 bytes of EPROM (erasable electrically programmable readonly memory). However, it should be appreciated that other suitablemicrocomputer chips or microcomputer circuits could be employed in theappropriate application. Similarly, the memory 3253 (chip Z141) may beany suitable memory chip or circuit having sufficient capability tostore the computer programs which operate in accordance with the controlmethodology discussed in detail above, such as an Intel 87C257 memorychip.

As will be appreciated from FIG. 4, the interface 3252 (chip Z135) maybe any suitable chip or set of chips/circuits which generally providethe circuits illustrated in this Figure. As will be discussed below, theinterface 3252 (chip Z135) includes several internal registers forfacilitating rapid communications between microcomputer 3251 (chip Z138)and several of the other circuits contained in the transmissioncontroller 3010, such as the pressure switch interface circuit 3240. Inthe present embodiment, the various circuits illustrated in FIG. 4 havebeen combined into a single chip configuration, namely interface (chipZ135), to conserve space on the circuit board for the transmissioncontroller 3010.

Each of the pins or ports of the various chips used in the micro core3250 have been appropriately labeled, so that the various circuitconnections between these chips and the other circuits contained in thetransmission controller 3010 may be readily discerned from each of theFIGS. 3A-3I. For example, the "Control" and "Idle" lines of thecommunication chip Z14 in FIG. 3A are also shown to be labeled "PA7" and"PD1" respectively. As will be appreciated from FIG. 3B, both of thesesignal lines are connected to the interface (chip Z135), as this chipcontains both the "PA7" and "PB1" labeled ports.

The microcomputer 3251 (chip Z138) and the interface 3252 (chip Z135)communicate with each other via an address/data bus labeled "ADΦ-AD7".The address/data lines in this bus are bidirectional to allow thetransfer of both address and data information between the microcomputer3251 (chip Z138) and the interface 3252 (chip Z135). As illustrated inFIG. 3C, the memory (chip Z141) is also connected to this address/databus. The memory (chip Z141) is also connected to the microcomputer 3251(chip Z138) via an address bus which is comprised of address lines"A8-A15". Three of these address lines, namely address lines A13-A15,are also connected to the interface 3252 (chip Z135) for selectingparticular register or RAM locations within this chip.

Referring to a portion of FIG. 3D, a schematic diagram of the speed andthrottle input circuits 3210 are shown. These circuits are designated as3212, 3214 and 3218. The speed input signals are labeled "N_(e) /Turbo","N_(e) ", "N_(o) " and "N_(t) ". The throttle input signals are labeled"THD-GND" and "THR".

The N_(e) /Turbo and N_(e) signals are used in an application involvinga turbo equipped engine, which provides a dual pick-up in thedistributor of the engine. In this situation, both the NE and NE/Turbosignals are used to indicated engine speed. However, while these signalsprovide the same engine speed data, these signals are out of phase witheach other. In this regard, it should be noted that in distributorshaving a single engine speed pick-up, only the N_(e) signal would beused by the transmission controller 3010. FIG. 3D shown that the inputinterface circuit for the N_(e) /Turbo signal comprises a low passfilter 3212, which includes resistor R91 and capacitors C90 and C32. Thefiltered NE/Turbo signal is then directed to the "PB2" port of theinterface 3252 (chip Z135). A similar filter network 3214 is alsoprovided for the engine speed signal "N_(e) ". However, an invertingamplifier Z15 is also included as a buffer to provide the fast rise andfall times required by the microcomputer 3251 (chip Z138), as well asnoise immunity.

The "N_(o) " input signal represents the output speed of thetransmission, while the "N_(t) " signal represents the input or turbinespeed of the transmission. These signals are first filtered and thentransmitted to a zero crossing detector circuit which includes thecomparator Z47. Due to the sensitivity of these signals (e.g., minimumamplitude of 500 millivolts peak to peak), each of the comparators Z47is provided with a positive feedback loop for adding hysteresiscapability to these zero crossing detector circuits. For example,resistor R49 and capacitor C48 provide this hysteresis capability forthe output speed signal N_(o). It should also be noted that the filtercircuits for these two speed signals use a ground signal labeled"A/GNB". This ground signal represents a clean ground signal which isderived from the microcomputer 3251 (chip Z138) to heighten thesensitivity of these filter circuits. Once the output speed signal N_(o)is properly conditioned, it is transmitted to the "IC2" port of themicrocomputer 3251 (chip Z138). In contrast, the conditioned inputtransmission speed signal N_(t) is transmitted to the " NTI" port of thewatchdog/reset chip Z127 (shown in FIG. 3C).

The THR and TH-GND signals are used to indicated the throttle positionin the vehicle. These signals are processed through a unity gaindifferential amplifier circuit, which is generally designated by thereference numeral 3216. This differential amplifier circuit is used tosense the ground potential of the throttle position sensor, as well assense the potentiometer wiper signal of this sensor. The output of thedifferential amplifier circuit 3216 is directed to the "PEΦ" port of themicrocomputer 3251 (chip Z138). Since the throttle position signal is ananalog input signal, it should be appreciated that the microcomputer3251 (chip Z138) includes an internal analog to digital converter topermit further processing of this signal in accordance with the controlmethodology discussed above.

This is further illustrated in conjunction with FIG. 8 where thedissimilar grounds of the engine controller 3020 and transmissioncontroller 3010 are graphically depicted. Attention is invited also tocircuit 3216 in FIG. 3D. Dissimilar grounds can generate a variablereference to ground. This is a function of variable resistance andinductance in the vehicle and its electrical system. The variable groundreference could be a significant percentage of the span of the outputvoltage from the throttle position sensor. Therefore, without thefeature of the shared throttle position sensor circuit, two sensorswould be needed.

FIG. 3D also shows a portion of the ignition switch interface circuits3220. Specifically, FIG. 3D shows the interface circuit 3218 for theignition switch signal "J2". The interface circuit 3218 provides a lowpass filter whose output is directed to the "FJ2" port of thewatchdog/reset chip Z127.

Turning to FIG. 3E, the last of the ignition switch interface circuits3220 is shown. Specifically, an interface circuit 3222 for the crankonly ignition signal "S2" is shown. The interface circuit 3222 includesa voltage divider (R78 and R80), a low pass filter (R61 and C79), and acomparator Z47. The voltage divider is used to decrease the voltagelevel of the S2 signal, so that it does not exceed the maximum inputvoltage of the comparator. The output of the comparator Z47 is connectedto the "FS2*" port of the watchdog/reset chip Z127. The S2 ignitionsignal is used to hold the microcomputer 3251 (chip Z138) in a resetmode during the cranking of the engine. This provision is implementedfor purpose of accuracy, since it is possible that the battery voltagein the vehicle could dip down during the cranking of the engine.

CIRCUIT FOR DETERMINING THE CRANK POSITION OF AN IGNITION SWITCH BYSENSING THE VOLTAGE ACROSS THE STARTER RELAY COIL AND HOLDING ANELECTRONIC DEVICE IN A RESET CONDITION IN RESPONSE THERETO

FIG. 3E also illustrates the PRNODDL interface circuits 3230.Specifically, FIG. 3E shows the circuits used to interface the neutralstart signals "NS1" and "NS2", as well as the circuits used to interfacethe reverse light signals "RL1" and RL2". Each of these signals aredigital signals which will generally be at a zero or battery voltagepotential. Accordingly, each of the interface circuits for the signalsinclude a pair of voltage dividing resistors (in addition to a filter)for getting the battery voltage level down to a 5 volt potential. Inthis regard, it should be noted that each of these input signals arecoupled to the ignition switch signal "J2" through suitable pull-upresistors (e.g., R82 and R83) to ensure that these signals will providebattery voltage potential when their corresponding switches are open.

While the conditioned NS1 signal is transmitted to the "PE5" port of themicrocomputer 3251 (chip Z138), this signal also provides a gatingsignal to the transistor Q93. The transistor Q93 is used to disable theS2 signal from causing a reset of the microcomputer 3251 (chip Z138). Inother words, when the contact switch NS1 is open, the NS1 signal will beHIGH, thereby causing the transistor Q93 to conduct and pull down theinput voltage to the comparator Z47. This provision is to ensure thatthe S2 signal does not cause a reset unless the transmission 100 iseither in neutral or in park. This is also graphically depicted in FIG.9 and its accompanying chart of the states of the contacts, devices andoutputs.

Referring to FIG. 3, a schematic diagram of the regulator circuit 3290and the relay driver circuit 3270 is shown. Additionally, FIG. 3F showstwo capacitors (C228-C233) which are used to tie the grounding potentialof the circuit board for the transmission controller 3010 to thealuminum case which surrounds the circuit board. This optional featuremay be used to provide additional RF or electromagnetic compatibilityfor the transmission controller circuitry.

DUAL REGULATOR

The regulator circuit 3290 shown in FIG. 3F generally comprises a dual 5volt regulator chip Z215 which receives a voltage input signal from thevehicle battery and a command signal from the watchdog/reset chip Z127.This command signal, labeled "PSENA*", is used to enable or switch onand off the "VO2" output of the regulator chip under MCU command whenignition is off. The VO2 output of this chip provide the "SW/5 V" supplysignal discussed above. This provision of a switchable 5 volt supply isparticularly advantageous in a vehicle application, as it permits asubstantial portion of the peripheral circuitry (or circuitry with a lowpriority) connected to the micro core 3250 to be shut down when thevehicle ignition is off thus reducing current draw on the battery. Thiscan also be used under conditions requiring an orderly shutdown forpurposes of storing last-sensed data etc. A continuous voltage outputcan be provided to high priority circuits such as a memory chip or aMCU. It can also be used to keep high priority circuits energized in a"KEY-OFF" situation, if desired, to allow for example the control ofgear selection/display while the engine is off.

SHUTDOWN RELAY DRIVER

The shutdown relay driver circuit 3270 includes a self protecting, highside switch chip Z219 which is responsive to a "RLYCNT" control signalfrom the watchdog/reset chip Z127. Specifically, the relay controlsignal will cause the battery voltage to be transmitted to the "VOUT"port of the switch chip Z219. This voltage output from the chip Z219 isreferred to as the "RELAY/PWR" signal, as it provides the powernecessary to operate the shut down relay 3272 shown in FIG. 5. The shutdown relay 3272 is used to cut power off to the solenoid driver circuits3280 to thereby achieve a "LIMP-IN" mode previously described.Specifically, when the shut down relay 3272 is closed, the "SW/BATT"signal shown in FIG. 3F will be transmitted to the solenoid drivercircuits 3280. However, before this SW/BATT signal is transmitted to thesolenoid driver circuits 3280 it is processed through conditioningcircuit 3274. The conditioning circuit 3274 includes a diode "D224"which is used to clamp the back EMF of the solenoid coils when the shutdown relay 3272 is open. The conditioning circuit 3274 also includes apull down resistor R225 to ensure that the line is pulled to grounddespite the states of the solenoid driver circuitry. A capacitor C223 isalso provided to suppress any line inductive energy spikes that mightoccur in response to the switching of the transmission solenoids.

THE USE OF DIODES IN AN INPUT CIRCUIT TO TAKE ADVANTAGE OF AN ACTIVEPULL-DOWN NETWORK PROVIDED IN A DUAL REGULATOR

It should be noted that both the "RELAY/PWR" and "SW/BATT" signalsprovide input signals to the conditioning circuit block 3310. In thepresent embodiment, the conditioning circuit block 3310 employs thickfilm packaging technology to effectively create a single compact chipfor the circuits contained in this block. The conditioning circuit block3310 is comprised of four identical conditioning circuits 3320-3350.Each of these conditioning circuits include an RC filter (R300 and C200)and a pair of voltage dividing resistors (R301 and R302). Since theSW/BATT and RELAY/PWR signals are at the battery voltage potential, thevoltage dividing resistors cut this voltage level down to the 5 voltlogic level used in the micro core 3250. This is also furtherillustrated in FIG. 6 which shows this concept in a simpler form.

It is also important to note that each of the conditioning circuits3320-3350 include a diode "D300" which connects the input signal of eachof these circuits to the SW/5V supply line. This is a particularlyadvantageous feature of the present invention, because the regulatorchip Z215 will actively pull the SW/5V signal level down to groundduring an over voltage condition (e.g., where the battery voltageexceeds 30 volts). Accordingly, the diode D300 will clamp the batteryvoltage level input signals to the conditioning circuits 3320-3350 downto ground during such an over voltage condition. This will preventexcessive input signals from being transmitted to the micro corecircuits 3250 via ESD protection diodes. In this regard, for example,the RELAY/PWR signal is transmitted to the "PBΦ" port of the interfacecircuit Z135 of the micro core 3250 through the conditioning circuit3330. This feedback provision will enable the microcomputer 3251 (chipZ138) to confirm the status of the relay driver circuit 3270 and is alsoused while testing the watchdog reset.

OPEN LOOP CONTROL OF AND SPIKE MONITOR FOR SOLENOID COIL DRIVERS

Referring to FIG. 3G, a schematic diagram of the solenoid drivercircuits 3280 is shown. The solenoid driver circuits 3280 comprise anindividual driver circuit for each of the four solenoid-actuated valves630, 632, 634 and 636 contained in the transmission namely, drivercircuits 3282-3288. Each of these driver circuits is provided with twoinput signals, one of which is derived from the interface 3252 (chipZ135) and the other of which is derived from the microcomputer 3251(chip Z138). For example, in the driver circuit 3282, an enablementcommand signal is transmitted form "PC6" port of the interface 3252(chip Z135), and a current control signal is transmitted from the "OC2"port of the microcomputer 3251 (chip Z138). The OC2 signal is derivedfrom an internal timer of the microcomputer 3251 (chip Z138).Specifically, the OC2 control signal generated by MCU timer functionsprovides a series of pulses which have an appropriate duty cycle forcausing a pulse width modulation of the current to the solenoid coil,such as the underdrive (UD) coil, in addition a "pull in" pulse is MCUtimer generated when the solenoid coil is first turned on.

When the microcomputer 3251 (chip Z138) causes the interface 3252 (chipZ135) to latch its "PC6" port into a HIGH state, the driver circuit 3282will be enabled through the gating on of transistors Q177 and Q169. Thegating on or HIGH pulse of the OC2 signal will permit the current in theUD solenoid coil to charge up through the transistor Q179. Then, whenthe pulse of the OC2 signal is turned off, current through the UDsolenoid coil will circulate in the path created by the diode D168 andtransistor Q169. The result will be an efficient slow decay of thecurrent through the UD solenoid coil. At this point, it should be notedthat the junction between the Darlington pair transistor Q169 and theMOSFET resistor Q179 will be at a potential above the potential of theSW/BATT supply signal.

Subsequently, when the microcomputer chip Z138 causes the "PC6" port ofthe interface 3252 (chip Z135) to switch to a LOW state, the transistorQ177 will switch off and cause a rapid decay of current through the UDsolenoid coil. When the gate signal is removed from the transistor Q177,it should be noted that the Darlington pair transistor Q169 will alsoturn off. This rapid decay of current will also cause the voltage on theconductor 3289 to rise above the SW/BATT potential. At some point (e.g.,25 volts), this rising potential will cause the Darlington pairtransistor Q169 to turn on again to limit the spike of this risingvoltage potential. However, it is important to note that the voltagepotential on conductor 3289 is transmitted through the diode "D174" tothe zener diode "D173". At a predetermined potential (e.g., 24 volts),the zener diode D173 will breakdown and cause current to flow throughthe transistor Q168 to the "PB3" port of the interface 3252 (chip Z135).

This spike monitor circuitry is an important aspect of the presentinvention, as it allows the microcomputer 3251 (chip Z135) to determinewhether the solenoid coil is in a shorted or open condition. In otherwords, the spike monitor circuitry of the solenoid driver circuits 3280will tell the microcomputer 3251 (chip Z138) that the solenoid coil hasindeed turned off. In this regard, it should be noted that the SW/BATTsignal continually keeps the transistor Q160 in an conducting condition,so that the current from conductor 3289 will pass directly through itsemitter and collector junctions for transmission to the "PB3" port ofthe interface 3252 (chip Z135).

It should be appreciated that the diode "D173" is connected to each ofthe driver circuits 3282-3288 through appropriate diodes (e.g., D175 andD202), so that the microcomputer 3251 (chip Z138) will be able to detectthe presence of a voltage spike from each of these driver circuits.While each of the driver circuits 3282 are substantially identical, theconnections employed in the driver circuit 3282 will be brieflydescribed.

The OC2 port of the microcomputer 3251 (chip Z138) is connected to thegate of the MOSFET transistor Q179 through the resistor R181. The sourceof the transistor Q179 is connected to ground, while the drain of thistransistor is connected to one end of the UD solenoid coil. The otherend of the UD solenoid coil is connected to the junction between theSW/BATT potential and the diode pair D168. The common emitter junctionof the Darlington pair transistor Q169 is connected across the reversebias diode in the diode pair D168, while the collector junction of thetransistor is connected to the drain of the MOSFET transistor Q179. Acapacitor C240 is coupled across the collector and base junctions of theDarlington pair transistor Q169 for stability, while a resistor R230 isconnected across the base and emitter junction of this transistor toprovide sufficient current for spike monitor operation. The base of thetransistor Q169 is also connected to the collector junction of thetransistor Q177 through the resistor R170. The base of the transistorQ177 is coupled to the "PC6" port of the interface circuit Z135 throughthe transistor R176. The emitter junction of the transistor Q177 isconnected to ground. The conductor 3289 is connected to the collectorjunction of the transistor Q177, and is coiled to the diode D174 throughone of the diodes labeled "D175".

FIG. 10 is an illustration of closed loop and open loop control ofsolenoid coil drivers showing basic differences between the circuits andbasic similarities between the voltage outputs. An electronic drivercircuit for the open loop control of the energization of a solenoidcoil, forming part of an electromagnetic solenoid actuator valve, inresponse to a control pulse produced by a control circuit and where thepredetermined schedules are a function of the inductance and resistanceof the coil, the desired peak output voltage from the coil and thedesired average holding current through the coil.

The principals of the injector driver circuit are also described inco-assigned U.S. Pat. No. 4,631,628, issued on Dec. 23, 1986, which isexpressly hereby incorporated by reference.

Referring to FIG. 3H, a schematic diagram of the pressure switchinterface circuits 3240 is shown. The pressure switch interface circuits3240 are generally embodied in a conditioning circuit block 3242 whichis identical to the conditioning circuit block 3310 in the presentembodiment. Thus for example, the conditioning circuit block 3242includes a conditioning circuit 3244 for the "KDPR-SW" pressure switchsignal. It should also be noted that the conditioning circuit block 3242includes a conditioning circuit 3246 which has an input signal labeled"CK/TRANS/LTG". This input signal is generated in the diagnostic alertcircuit 3500 shown in FIG. 3I.

Referring to FIG. 3I, the diagnostic alert circuit 3500 is shown to beprovided with an input signal labeled "FSW/BATT", which represents thefiltered battery voltage level produced at the output of theconditioning circuit 3320 shown in FIG. 3H. As discussed previously, theSW/BATT signal indicated that the battery voltage is being supplied tothe solenoid driver circuits 3280. The conditioning circuit 3320 is usedto drop this voltage level down to a usable 5 volt logic level which isfed back to the "PC7" port of the interface 3252 (chip Z135) through thediode "D162" of the diagnostic alert circuit 3500.

The FSW/BATT signal is transmitted through an inverting amplifier Z15which is used to gate the MOSFET transistor Q165. The transistor Q165produces the CK/TRANS/LTG signal which may be used to alert the operatorthat power has been cutoff from the transmission solenoid-actuatedvalves 630, 632, 634 and 636, such as through a light on a diagnosticpanel in the passenger compartment. In an application involving the useof the diagnostic alert circuit 3500, the conditioning circuit 3246shown in FIG. 3H will provide a feedback signal to the "PA1" port of theinterface 3252 (chip Z135) to confirm that the diagnostic panel has beenprovided with the appropriate signal.

FIG. 3I also shows an additional communication circuit 3400 whichprovides a direct serial transmission link from the transmissioncontroller 3010 to the engine controller 3020. Such a separatetransmission channel may be employed when it is desired to send highpriority or rapid signals to the engine controller 3020. For example, insome applications it may desirable for the transmission controller 3010to advise the engine controller 3020 that a gearshift is about to takeplace. In such a situation, the microcomputer 3251 (chip Z138) wouldcause an appropriate signal to be placed on the "PB7" port of theinterface 3252 (chip Z135) to gate on the transistor Q243. The gating onof the transistor Q243 will generate the "TRDLINK" signal through thefilter network comprised of resistor 245 and capacitors 244 and 246.

Referring again to FIG. 3H, the test mode circuit 3300 is shown toinclude the conditioning circuit 3350. When a testing mode for thetransmission controller 3010 is desired, the "test" input signal will beHIGH, thereby causing a LOW "modea/lir" signal to be transmitted to themicrocomputer chip Z138. This signal will cause the microcomputer chipZ138 to initiate the test mode sequence discussed above.

Referring to FIG. 4, a block diagram of the interface chip Z135 isshown. The pin designations shown in this figure (e.g., "PC0-PC7")generally correspond to the pin designations shown for the interface3252 (chip Z135) in FIG. 3B. There is one exception to thiscorrespondence. In FIG. 3B, the pins for Port-A are designated"AD0-AD7"; whereas, in FIG. 4, these pins are designated "D0-D7".

In addition to Port-A, the interface chip Z135 also includes two otherports, namely Port-B (i.e. pins PB0-PB7) and Port C (i.e. pins PC0-PC7).Pins PB0-PB3 of Port-B are connected to the edge detect input circuits3600. The edge detect circuits 3600 provide a way to capture theoccurrence of an event, such as the turning off of a coil of asolenoid-actuated valve, at a time when the microcomputer 3252 (chipZ138) might otherwise be occupied. Thus, for example, pin PB3 of theinterface 3252 (chip Z135) is connected to the spike monitor circuitryof the solenoid driver circuits 3280 in order to transmit a signalindicative of the turning off of a coil of a solenoid-actuated valve tothe microcomputer 3251 (chip Z138) through interface 3252 (chip Z135)can generate an interrupt signal IRQ* which will inform themicrocomputer 3251 (chip Z138) that event information has been receivedfor further processing.

The interface 3252 (chip Z138) also includes a plurality of countdowntimers 3602, which are responsive to the "E" clock signal of themicrocomputer, through the E-clock prescaler circuit 3604. The outputfrom these timers may be transmitted to pins PB4-PB7 through the timeroutput circuitry 3606, in the event that the timer features of theinterface chip are desired to be employed. Otherwise, the pine PB4-PB7may be used as general purpose output pins.

While Port-C of the interface 3252 (chip Z135) could be used as a loworder address port, the mode select signal "MS" is used in the preferredembodiment to configure this port s an output port. In thisconfiguration, the address strobe signal "AS" from the microcomputerchip Z138 is used to command the address latch 3608 to capture low orderaddress information at AD0-AD7 of the interface 3252 (chip Z135.).

The interface 3252 (chip Z135) also includes a random access memorycircuit 3610, a plurality of internal registers 3612 and a decoder logiccircuit 3614. Particular locations in the RAM 3610 and particularinternal registers 3612 may be accessed through the decoder logiccircuit 3614, which is responsive to the address signal pins "A13-A15"in addition to the latched low order address A₀ -A₇. The internalregisters 3612 are used to provide access and control of the variousports and counters for the interface 3252 (chip Z135).

Referring to FIG. 5, a block/schematic diagram of the watchdog/resetcircuit Z127 is shown in association with some of the circuits connectedto the watchdog/reset circuit Z127. The first function of thewatchdog/reset or "WD" circuit is to monitor the operation of themicrocomputer 3251 (chip Z138) by requiring the MCU to periodicallytransmit a signal to the WD circuit. This signal is designated "WDG"inboth FIGS. 28C and 5. If the WD circuit does not receive the WDG signalwithin a predetermined time window, then the WD circuit will know thatthe MCU may not be functioning as desired. However, before the WDcircuit will react tot his situation, it will wait a predeterminedamount of delay time to see if proper functioning of the MCU will bequickly restored. If the WDG signal is not received by the end of thedelay period, then the WD circuit will transmit a "RLYCNT" signal to therelay driver circuit Z219 which will cause the shutdown relay 3272 toremove electrical power from the solenoid driver circuit 3280.

In this regard, FIG. 5 shows that the WD circuit includes a windowdetector circuit 3700 which receives the WDG signal. The window detectorcircuit 3700 includes an up counter which is reset by the WDG signal,and a pair of comparators which determine whether or not the WDG hasbeen received within the predetermined time window (e.g., 14 ms.). Ifthe WDG signal is received too early or too late, or not received atall, then the Q output of the window detector will switch to a LOWdigital state. This will in turn drive the output of AND gate 3702 LOW.

The output of the AND gate 3702 is connected to a fault delay circuit3704 and to a conductor 3706. The fault delay circuit 3704 will give theMCU a predetermined time period (e.g. 64-512 ms.) to transmit the WDsignal. This time period may be altered between four different valuesdepending upon the particular voltage or ground connections for theinput signals "DLYA" and "DLYB". In the meantime, the conductor 3706will transmit the "WDFLT" feedback signal, and provide a way ofseparately testing the operation of the window detector 3700 and thefault delay circuit 3704 within the WD circuit. The conductor 3706 isconnected to an input of the AND gate 3702 through the resistor 3708 andconductor 3710. To test the fault delay circuit 3704, the MCU willtransmit the "DLY/MON" signal, which will drive the AND gate 3704 LOW inorder to simulate the absence of the WD signal from the window detectorcircuit 3700.

If the WD signal is not received within the time period controlled bythe fault delay circuit 3704, then the AND gate 3712 will switch states,and cause the relay driver circuit Z219 to cut off power through thelogic connections provided by OR gate 3714 and AND gate 3716. The ANDgate 3712 also receives a "Latchdown" signal from the relay drivercircuit, which will prevent the AND gate 3712 from switching statesagain until the reset start-up sequence is initiated, even if the MCUtransmits a proper WDG signal in the intervening time period. In otherwords, once the WD circuit Z127 causes the relay driver circuit Z219 toremove electrical power from the solenoid driver circuit 3280, the resetstart-up sequence must be initiated before power will be restored to thesolenoid driver circuit.

The WD circuit is also responsive to a master kill signal "MK" from theMCU for removing power from the solenoid driver circuit 3280. In otherwords, when the MCU determines that power should be removed for whateverreason, then the MK signal will be transmitted to the relay drivercircuit through the AND gate 3716.

Another function of the WD circuit Z127 is to control the reset start-upsequence which will occur, for example, when electrical power is firstapplied to the transmission controller 3010. When power is firstapplied, this sequence will be initiated by the master reset signal"MRST", which is derived from an RC delay off the VDD power supply.

The reset start-up sequence may also be initiated from a filtered doorentry signal "FENTRY". This optional feature could be provided when itis desired, for example, to have the vehicle electrically display thecurrent PRNODDL transmission mode in response to the opening of thevehicle door, prior to the time that the key is inserted into thevehicle ignition. The reset start-up sequence may also be initiated froman actuation of the ignition key, via the ignition signal "FJ2".

The WD circuit includes a pair of one shot multivibrators 3718-3720,which will generate a single or one shot pulse output whenever theFENTRAY or FJ2 signals are received. The output from one shot 3718 iscombined with the FJ2 signal at the AND gate 3722, while the output ofthe one shot 3720 is fed directly to the NOR gate 3724. The output fromthe NOR gate 3724 is connected to the reset input to the counter 3726.Accordingly, it should be appreciated that the NOR gate 3724 serves tocombine all those inputs which can cause a reset condition to begenerated.

The counter 3726 will generate the reset signal "MPURST", which will betransmitted to the MCU through the buffer 3728. The counter 3726 willalso generate a false OK signal on conductor 3730, which is necessary tooverride or reverse the Latchdown signal. Thus, in the situation wherethe Latchdown signal has been generated, the momentary false OK signalwill allow re-enablement of the relay driver circuit Z219 through ORgate 3714 and AND gate 3716. This re-enablement will, in turn, overridethe state of the Latchdown signal, and permit electrical power to thesolenoid driver circuit 3280 to be applied.

While the above described reset start-up sequence will cause only amonetary MPURST signal to be transmitted to the MCU, the WD circuit alsoincludes a provision for maintaining the presence of this reset signalin response to predetermined regulator conditions. In this regard, itshould be appreciated that the continued presence of the reset signalwill disable the operation of the MCU, until proper operation of theregulator is restored and the reset signal is removed (i.e. the digitalstate of this signal is changed).

THE UTILIZATION OF A RESET OUTPUT OF A VOLTAGE REGULATOR AS A SYSTEMLOW-VOLTAGE INHIBIT

As shown in FIG. 5, the regulator circuit Z215 will generate a powersupply reset signal "PSRST", which will be transmitted to the NOR gate3724 through the AND gate 3730. This power supply reset signal will begenerated whenever the input voltage to the regulator is too low or toohigh, or when the regulator is being overloaded.

This feature provides for increased system integrity by holding the MCU3251 and the transmission controller 3010 in a predetermined RESET stateunder certain conditions including those shown in conjunction with FIG.7.

Here a reset output is generated on the powering down of a switch. Inother words, the "peripherals" are reset on power-up.

An "additional" RESET mode is provided by the regulator (as shown inFIG. 7) that must be gated out through the watchdog/reset circuit shownin FIG. 5; it also responds to the switching off of the second voltageregulator signal.

Another function of the WD circuit Z127 is to divide the turbine speedsignal "N_(t) " down so as to reduce the interrupt burden on the MCU.Accordingly, the WD circuit includes a programmable frequency divider3732 which receives the turbine speed signal N_(t). The divide controlsignals "DIVA" and "DIVB" from the MCU are used to determine one of fourdifferent divide ratios to be employed by the divider 3732.

It should also be noted that the WD circuit includes a block 3734 whichis labeled "prescaler/system clocks". This block comprises a timer witha prescaler which is used to provide both reset and start-up times, aswell as the fault delay and window detector clock signals employed inthe WD circuit.

The resent invention has been described in an illustrative manner. It isto be understood that the terminology which has been used is intended tobe in the nature of words of description rather than of limitation.

Obviously, many modifications and variations are possible in light ofthe above teachings. Therefore, the subject invention may be practicedotherwise than as specifically described.

What is claimed is:
 1. An electronic driver circuit for open loopcontrol of the energization of a solenoid coil, forming part of anelectromagnetic solenoid actuator valve, in response to a control pulseproduced by a control circuit, comprising:a microcomputer unit (MCU); amemory to work with the MCU and to store predetermined schedules ofsolenoid coil energization "ON" time; switching means having a pluralityof predetermined states to make or interrupt the current flow to thesolenoid coil according to the predetermined schedules an din responseto a control pulse; means providing an electrical path for circulatingcurrent in the solenoid coil to produce slow decay of the currentthrough the solenoid coil in response to tone of said plurality ofpredetermined states of said switching means; and means for producing arapid decay of current through the solenoid coil in response to anotherof said plurality of predetermined states of said switching means toallow the MCU to rapidly turn off the solenoid coil.
 2. The circuit ofclaim 1 where the predetermined schedules are a function of theinductance and resistance of the coil.
 3. The circuit of claim 1 wherethe predetermined schedules are a function of a desired peak outputvoltage from the coil.
 4. The circuit of claim 1 where the predeterminedschedules are a function of a desired average holding current throughthe coil.
 5. The circuit of claim 1 where the predetermined schedulesare a function of a desired peak output voltage from the coil; andof adesired average holding current through the coil.
 6. An electronicdriver circuit for open loop control of the energization of a solenoidcoil, forming part of an electromagnetic solenoid actuator valve, inresponse to a control pulse produced by a control circuit, comprising:amicrocomputer unit (MCU); a memory to work with the MCU and to storepredetermined schedules of solenoid coil energization "ON" time;switching means to make or interrupt the current flow to the solenoidcoil according to the predetermined schedules and in response to acontrol pulse; means providing an electrical path for circulatingcurrent in the solenoid coil to produce slow decay of the currentthrough the solenoid coil in response to one of said plurality ofpredetermined states of said switching means; and means for producing aseries of pulses having a predetermined duty cycle for causing a pulsewidth modulation of the current to the solenoid coil and for producing apull-in pulse at the start of the energization "ON" time for thesolenoid coil.